Bird depredation of fish, crawfish, and shrimp in aquaculture ponds poses major problems. For example, pelicans can consume 1 to 3 lb (0.45 to 1.36 kg) of fish per day, and may arrive with hundreds per flock. Cormorants, anhingas, herons, and egrets may also do significant damage to aquaculture ponds. It is estimated that one egret can eat ⅓ lb (0.15 kg) of fish per day, while a great heron can eat ⅔ to ¾ lb (0.30 to 0.34 kg) per day. See G. A. Littauer etal., “Control of Bird Predation at Aquaculture Facilities: Strategies and Cost Estimates,” Southern Regional Aquaculture Center, Publ. No. 402 (1997). This problem can be especially troublesome in ponds that have just been stocked with young fish.
M. D. Hoy et al., Eastern Wildlife Damage Control Conference, vol. 4, pp. 109–112 (1989), estimated that wading birds could cause profound losses during fall migration, up to $10,000 per week on bait fish farms. The Louisiana State University Ben Hur Aquaculture Facility in Baton Rouge, La. recently experienced this problem with the white pelican during December 2000, when many fish were eaten and several ponds were completely de-stocked of fish.
A. R. Stickley et al., Eastern Wildlife Damage Control Conference, vol. 4, pp. 105–108 (1989), estimated that in 1988 catfish losses due to double-crested cormorants amounted to $3.3 million.
Currently, several different methods are employed to attempt to scare birds from aquaculture ponds. One of the most common methods is the use of sonic cannons. Sonic cannons emit loud bursts of noise. However, birds eventually become accustomed to the noise emitted by sonic cannons. Also, the loud “boom” produced by the sonic cannon can be disturbing to surrounding communities, and typically causes birds to migrate to other parts of the farm where the noise is more tolerable. See M. Bomford et al., “Sonic Deterrents in Animal Damage Control: A Review of Device Test and Effectiveness,” Wildlife Society Bulletin, vol. 18, pp. 411–422 (1990).
Poisons, scarecrows, and nets have also been used. However, these methods have several faults. For example, poisons are usually fatal to birds and may cause casualties in non-target species. Scarecrows are effective for short-term periods only, because birds typically adapt and become accustomed to them. Nets typically have a high initial cost and are not practical for large ponds (>5 acres/˜2 hectares).
An unfilled need exists for a cost-effective device and method for effectively reducing bird predation of aquatic organisms over a relatively long period of time. The device should be environmentally friendly, harmless to birds, and capable of withstanding expected environmental elements (e.g., water, wind, sun, and rain) and animal attacks. The device should also be able to endure biological challenges (e.g., wind, weeds, and slime), and should have some level of intelligence to adapt to the evolving conduct of birds.